This project has two long-range objectives. It seeks an understanding of the interactions among the excited states leading to efficient intersystem crossing in carbonyl compounds. It also studies the intramolecular processes which affect the phosphorescence quantum yield. Specificly, we propose to proceed on three directions: 1. Pursue the proton and 13C ENDOR studies of benzophenone in its phosphorescent triplet state. This investigation will lead to reliable information on the spin distribution of the molecule. 2. Employ the new technique of time-resolved magnetic resonance in elucidating the nature of the emitting species in a neat crystal of benzil at room temperature. 3. Examine the feasibility of applying the time-resolved magnetic resonance technique to molecules in a slowly tumbling liquid.